Is the GOG version of this censored or uncensored? I recall that in the uncensored version, the demons you're shooting are clearly nazis, and my girlfriend wants to play that version because she hates nazis as one ought to. So which is it?

Also, has anyone played this with John Romero's new .WAD One Humanity on Ubuntu Linux 20.04? That's what my gf uses and I want to be sure this will work for her.

It sounds like you are talking about Wolfenstein and not Doom. Wolfenstein was censored for having references to Nazis, but that was only in Germany, and that ban has been repealed recently.

From what I understand, DOOM also contains references to nazis. I am in fact talking about the game series where you fight demons on Mars.

Doom II has a single secret Wolfenstein level, which doesn't appear to be censored. Can't remember if Final Doom or the Master Levels have anything, but if they do, I think it's safe to assume they're also uncensored.

AFAIR, DOSBoxed versions of these games, sold on both GOG and Steam, never actually been censored. It's DOOM3 BFG Editiotn and the newer Unity-port where censorship of the classic levels took place. I didn't played it but know that, regardless to the OS used, you need at least a source port from the 'Limit removing' category to run the PWAD properly. And DOSBoxed vanilla engine is not suitable for this task.

The DOSbox version is uncut, the levels you are thinking of are 2 in Doom 2 and they are uncut.